Hi,
I don't think the VPN is the problem here but the fact that you can't bridge an interface running in adhoc mode. Ad-hoc is "lacks" a field in the wifi header which makes bridging impossible. However, I agree with your proposed solution - another router connected to the Ethernet of the wrt54g can solve the issue.
This is not possible in this case (I don´t have another router).
Does Franco have another router which he could connect to the wrt54g?
Is there onother (maybe harder) way or a hack to do get the same result like when bridging two interfaces? Maybe with iptables?
I think this would break our setup.
Or does anyone know what the status of multiple ssid on wrt54g with kernel 2.6 is?
Maybe we should ask here: http://wireless.kernel.org/en/users/Drivers/b43#support
I have no experience with brcm-chips due to I have only a brcm4318 in my laptop.
regards Bjoern